From the German Pat. No. DE 2 734 729 there is known a measurement transformer in which a magnetic core surrounds a current-measuring conductor (the measurement transformer) in a tongue-like manner, and includes a pre-magnetizing winding. External to the pre-magnetizing winding passage of the magnetic flux through the magnetic core is impeded by an air gap, which is bridged by a very thin magnetic film. When the magnetic field, generated by an alternating pre-magnetizing current, and the measuring current, crosses zero, the magnetic film is re-magnetized into an opposite direction of saturation, which in turn induces an output pulse in the pre-magnetizing winding. Any deviation of the output pulse from its normal time position, (in the absence of any current passing through the current-measuring conductor,) represents an indication of the magnitude of the current to be measured, which passes through the measuring conductor. The theoretical basis for the aforenoted measurement principle is discussed in the IEEE Transactions on Instrumentation and Measurement, Vol. IM-21, Nr. 4, November 1972, pp. 346-349.
No prior art is known which optimizes the constructional features of a measurement transformer of the aforedescribed kind, although pot-shaped magnetic cores are known from the ITT Reference Data for Radio Engineers, pages 13-21, published by Howard W. Sams & Co.